Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
  • C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
  • C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
  • C07C37/72—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by liquid-liquid treatment

Definitions

• Resorcinol-formaldehyde condensation products with a low average molecular weight i.e. oligomers of resorcinol and formaldehyde (so-called resorcinol precondensates), are used, among other things, as adhesion promoters between textile cord or steel fibers and rubber in rubber articles containing these reinforcing agents, such as tires, drive belts, conveyor belts and rubber hoses, used.
• these resorcinol precondensates as adhesion promoters is preferable to that of pure resorcinol, since their vapor pressure is substantially lower than that of the resorcinol and thus prevents the resorcinol from sublimating out of the hot rubber mixture.
• JP-Laid-Open Application 82/143 316 already discloses a process for producing resorcinol precondensates with a relatively low residual free resorcinol content, the resulting crude resorcinol precondensate melt being extracted with xylene to deplete the resorcinol in particular.
• the viscosity of the resorcinol precondensate melt increases sharply with a decreasing resorcinol content.
• the lowering of the viscosity by increasing the temperature is limited by the noticeable occurrence of decomposition products above 110 * C.
• the invention therefore relates to a process for separating free resorcinol from oligomeric resorcinol precondensates by solution extraction, characterized in that the separation is carried out by continuous solution extraction using two immiscible liquid phases according to the van Dijck process ( Distribution).
• the invention also relates to a process for the extractive separation of free resorcinol from oligomeric resorcinol precondensates, by solution extraction, characterized in that the separation is carried out by continuous solution extraction using ether, preferably diisopropyl ether and water as extraction phases.
• the crude, still free resorcinol-containing resorcinol precondensates used for cleaning can be prepared by any method, e.g. according to the process of DE-Offenlegungsschrift 40 02 417.2 or according to conventional processes in a homogeneous phase, e.g. described in A. Knop and L.A. Pilato, "Phenolic Resins", Springer Verlag, Berlin 1985, pages 90 to 300.
• resorcinol precondensate of free resorcinol.
• these resorcinol precondensates are used in the form of solutions for the cleaning process according to the invention, wherein ethers, in particular diisopropyl ether, can preferably be used as solvents for this.
• the average molecular weight of these resorcinol precondensates is not critical and can vary in the range typical for oligomers. It is preferably between approximately 230 and approximately 500, in particular between approximately 280 and approximately 420 (weight average).
• the ether / water system is preferably used as the liquid, immiscible phases, the total ether preferably containing at least 4 carbon atoms, in particular 4 to 18 carbon atoms.
• the quantitative ratio between ether, preferably diisopropyl ether, and water is generally between 1: 3 and 1:20, preferably between 1: 8 and 1:12.
• the process according to the invention is preferably carried out at room temperature, although moderately elevated temperatures up to about 90 ° C., especially up to about 50 ° C., are also possible. In general, work is carried out at normal pressure; in special cases, however, increased or reduced pressure can also be used.
• the usual extraction devices such as mixer-settlers, extraction columns with vibrating trays, with rotating or permanently installed trays, simply pulsating packed columns, mixing settlers, Graesser extractors, centrifugal extractors and the like are apparatuses for the extraction.
• suitable in which the raw mixture is fed in the middle and the extractants are guided in countercurrent.
• the ratio of the feed amount of the solution of the crude resorcinol precondensate to the feed amount of the ether is generally 1: 2 to 2: 1, preferably 1.5: 1 to 1: 1.5. Other proportions are also possible; these can easily be determined by a person skilled in the art and are dependent on the desired degree of extraction, the extractants used and the composition of the raw mixture.
• concentration of the crude resorcinol precondensate added to the extraction device in the solvent preferably one of the above ethers, is advantageously at most 50% by weight, preferably 20 to 40% by weight.
• the quantitative ratio of precondensate solution: ether: water according to the invention is usually 0.5 to 1.5: 0.5 to 1.5: 8 to 14, preferably 0.75 to 1.25: 0.75 to 1.25: 10 until 12.
• performing the extraction once in the extraction device is sufficient to obtain a resorcinol precondensate of the desired purity.
• the number of stages is generally at most 10, preferably 4 to 6. If necessary, if a particularly low residual resorcinol content is desired, this extraction separation can be repeated after the resorcinol precondensate has been isolated and a correspondingly concentrated solution has been prepared.
• a solution of the crude resorcinol precondensate in ether, preferably diisopropyl ether is pumped into the center of a countercurrent extraction column at room temperature and distributed therein in a multi-stage manner in a countercurrent bed of water and ether, preferably diisopropyl ether.
• water flows as a continuous phase from top to bottom, while the ether is conducted as a disperse phase from bottom to top.
• the quantitative ratio of ether, preferably diisopropyl ether, to water is between 1: 8 and 1:12.
• the resorcinol precondensates are isolated by evaporation of the ether from the ether (diisopropyl ether) / resorcinol precondensate phase running at the upper end. Small amounts of water dissolved in the ether phase go off as an azeotrope with the ether (diisopropyl ether; bp 62.2 ° C; 4.5% by weight water). The ether (diisopropyl ether) is then returned to the extraction. The resorcinol-containing water phase running off at the lower end of the extraction column is subjected to a separate resorcinol extraction and then also runs back into the extraction in a circuit.
• the resorcinol extraction of the water phase is preferably carried out with diisopropyl ether, and the resorcinol / diisopropyl ether phase obtained in this way is then returned to the manufacturing process of the resorcinol precondensate after the resorcinol content has been increased accordingly.
• the residual content of free resorcinol in the resorcinol precondensate can easily be adjusted via the quantitative ratio of the two liquid extraction phases and the number of stages of the extraction.
• the resorcinol precondensates cleaned according to the invention are suitable, for example, in combination with formaldehyde-releasing compounds in vulcanizable rubber mixtures which contain reinforcing agents based on textile fibers or steel cords for improving the adhesion between rubber and the textile or steel cords in the vulcanizates. Due to the low vapor pressure of the resorcinol pre-condensates cleaned according to the invention, which is comparatively too free, the exhaust air pollution by toxic substances, as is known Lich occurs when using free resorcinol due to the high processing temperatures required in the production of vulcanizable rubber compounds, greatly reduced.
• Diisopropyl ether was added as the disperse phase at the lower end of the column, and tap water as the continuous phase at the upper end.
• the quantitative ratio of precondensate solution: diisopropyl ether: water was 1.03: 1.0: 12.75.
• the diisopropyl ether phase running at the top of the column contained 11.25% by weight of resorcinol precondensate and 0.31% by weight of resorcinol, and the water phase running at the bottom end contained 0.78% by weight of resorcinol and 0.25% by weight.
• -% resorcinol precondensate The resorcinol precondensate phase was freed from the diisopropyl ether in the thin-layer evaporator and the melt obtained was then pelletized. The ether was returned to the process.
• reaction solution of 3.8% by weight of resorcinol and 20.95% by weight of resorcinol precondensate, based in each case on the solution in diisopropyl ether, was placed in the middle of a 7-stage laboratory mixer at room temperature (as in DE patent application P 39 13 779.1 described).
• the quantitative ratio of pre-condensate solution: diisopropyl ether: water was 1: 1.4: 12.6.
• the water phase running out at one end of the mixing settler contained 0.26% by weight resorcinol and 0.19% by weight resorcinol precondensates, and the diisopropyl ether phase running out at the other end contained 0.22% by weight resorcinol and 7.73% by weight .-% precondensates.
• reaction solution of 9.8% by weight of resorcinol and 26.4% by weight of resorcinol precondensate, in each case based on the solution, in diisopropyl ether was placed at room temperature in the middle of a pilot plant's moving-bottom column (3 m long, 50 mm inside diameter, 30 sieve trays, type Karr).
• Diisopropyl ether was added as the disperse phase at the lower end of the column, and tap water as the continuous phase at the upper end.
• the quantitative ratio of reaction solution: diisopropyl ether: water was 1.0: 1.0: 10.0.
• the diisopropyl ether phase running at the top of the column contained 13.1% by weight of resorcinol precondensate and 0.08% by weight of resorcinol, and the water phase running at the bottom end contained 0.97% by weight of resorcinol and 0.045% by weight. % Pre-condensate.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6415806

Family Applications (1)

Country Status (3)

Citations (5)

• 1991
  • 1991-10-02 EP EP91116857A patent/EP0480308A1/fr not_active Withdrawn
  • 1991-10-07 JP JP25940091A patent/JPH04247047A/ja not_active Withdrawn
  • 1991-10-07 CA CA002052904A patent/CA2052904A1/fr not_active Abandoned

Patent Citations (5)

Also Published As

Similar Documents

Legal Events